1. Technical Field
One or more embodiments of the present invention relate to a DC-DC converter. Particularly, one or more embodiments of the present invention relate to a DC-DC converter that can compensate a voltage drop caused by a wiring resistance.
2. Related Art
Two types of batteries, namely, a high-voltage battery and a low-voltage battery are usually provided in an electric-powered vehicle such as an EV (Electric Vehicle), an HEV (Hybrid Electric Vehicle), or a PHEV (Plug-in Hybrid Electric Vehicle).
The high-voltage battery is mainly used as a power supply for a load of a high voltage (hereinafter, referred to as a high-voltage load), such as a main power motor for driving wheels of the electric-powered vehicle to travel and a compressor motor of an air conditioner. On the other hand, the low-voltage battery is mainly used as a power supply for a load of a low voltage (hereinafter, referred to as a low-voltage load), such as a motor for various ECUs (Electronic Control Units), EPSs (Electric Power Steerings), electric brakes, car audio devices, windshield wipers, and power windows, or an illumination lamp.
The low-voltage battery is usually charged so that a DC-DC converter transforms a voltage at the high-voltage battery to supply the transformed voltage to the low-voltage battery. When a large voltage drop is generated by a wiring resistance between the DC-DC converter and the low-voltage battery, in order to stably charge the low-voltage battery, it is necessary to control an output voltage of the DC-DC converter to compensate the voltage drop.
Therefore, conventionally, the DC-DC converter and an input terminal of an electronic device that is a load thereof are connected by a cable dedicated to detecting the voltage, the voltage inputted to the electronic device is directly measured, and control is performed such that the measured input voltage becomes a desired value, thereby compensating the voltage drop caused by the wiring resistance (for example, see Japanese Unexamined Patent Publication No. 2003-274641).
In the DC-DC converter disclosed in Japanese Unexamined Patent Publication No. 2003-274641, the output voltage of the DC-DC converter is controlled such that an output current and the voltage drop caused by the wiring resistance are compensated according to the output current of the DC-DC converter. Similarly to the DC-DC converter disclosed in Japanese Unexamined Patent Publication No. 2003-274641, Japanese Unexamined Patent Publication No. 2006-180603 proposes that, in addition to controlling the output voltage to compensate the voltage drop according to the output current, a voltage correction coefficient can be adjusted with respect to the output current using a variable resistance such that the wiring resistance can cope with a plurality of devices.
However, when the output voltage is controlled by directly measuring the input voltage of the load of the DC-DC converter, it is necessary to provide the additional wiring connecting the DC-DC converter and the load, and necessary cost increases.
Moreover, in the DC-DC converter disclosed in Japanese Unexamined Patent Publication No. 2006-180603, it is necessary that the wiring resistance of the device to which the DC-DC converter is applied be previously measured to adjust a variable resistance value in each device.